SummaryThe present paper describes a development of hull-form database which can comprehensively include propulsive performances, dead weights, gross tonnages and general arrangement plans, and a verification of the effectiveness of the database for hull-form design. The present database focuses on 749GT-type domestic general cargos, which are subject to restrictions on the gross tonnage by a domestic law. The collaborative work with the shipyard had made the database more practical and more competitive than before. The towing tank test result shows the high performance of the developed standard hull-form which reaches design speed of 12.00 knots at about 61% MCR, even installed about 20% smaller main engine than the conventional one.Firstly, the design space of the database was carefully determined by the construction record of 749GT-type domestic general cargos, which have 3 design parameters with ship length, breadth and draft. 463 hull-forms were generated by hull-form blending (morphing) technique based on 8 basic hull-form. To reduce the wave resistances of its hull-forms effectively, CB and LCB of 8 basic hull-forms, which define the shapes of the sectional area curves, are formulated by the 3 design parameters.The relationships between CB and wave resistance, form factor and self-propulsion factor, respectively were discussed based on the evaluated results of propulsive performances in the view of the effect of increasing the diameter depending on draft. After the 51 hull-forms were selected by the practicality of propulsive performance, we evaluated dead weights and gross tonnages. The integrated evaluation of propulsive performance and dead weight indicates the trade-off relationship to the optimum ship length and breadth.To solve this problem more designer-friendly, we propose integrated hull-form database and an example of visualization (visualization useful for design), which enables multifaceted and quantitative design discussion. The advantage of this method over the multi-objective optimization methods is the capability to provide multifaced and highly effective information for decision making in the design process. The design verification about practical design discussion on the trade-off problem is shown the effectiveness of the integrated hull-form database.

On prediction of ship performance in actual seas, it is important to estimate external forces acting on a ship. The predominant factor is added resistance in waves which reduces ship speed. Therefore, added resistance in waves is required to be calculated with accuracy. In addition, since a ship sails with a drift motion due to winds and waves, it is required to estimate hydrodynamic forces and moment due to drift motion. As ocean waves is characterized their irregularity which contains various frequency and direction component, it is required to estimate added resistance in oblique waves as well as in heading waves. In this paper, it is investigated by tank tests whether the calculation method on added resistance in heading waves is applied to that in oblique waves. Furthermore, hydrodynamic forces and moment due to drift motion is calculated with appending a term of drag for wing of a small aspect ratio. The effectiveness of the calculation methods is shown by estimating decrease of ship speed in actual seas.

Estimation of ship speed in actual seas is very important to evaluate the comprehensive performance in her life. Estimation of the added resistance in ballast condition is more difficult than that in full load condition due to the complicated phenomena around the bulbous bow. The proposed method, which combines tank tests with calculation, shows the estimation of added resistance in ballast condition accurate for a Panamax bulk carrier. In this paper, the proposed method is applied to a handy-size bulk carrier (approximately 160m length) equipped with cranes in both ballast and full load conditions, and its accuracy is confirmed by model tests and onboard measurements. Moreover the difference of resistance components due to winds and waves is discussed in terms of load condition toward the improvement of evaluation of performance in actual seas for handy-size bulk carriers equipped with cranes.

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